Many chemical processes are conducted by flowing fluid reactants, such as a gas and a liquid, through a reactor vessel filled with a solid, such as a solid catalyst. In these processes, the efficiency of the chemical reaction is dependent upon how uniform the fluid flowing through the vessel is distributed. Therefore, the ability to measure the liquid distribution in a packed bed reactor is particularly useful in designing and operating these reactors.
In U.S. Pat. No. 4,750,357, there is disclosed a method of measuring local fluid flow rates in a packed catalytic reactor which is equipped with heated thermocouple probes. In operation, a temperature measurement is obtained first with the heater off and then a second temperature measurement is obtained with the heater on. The difference between the two temperatures is used to calculate the thermal mass flux. This procedure, of course, requires time to line out the probe for each step and permits measurement only at discreet time intervals. Thus, there remains a need for an improved method and apparatus that is capable of operating continuously and which provides a measure of mass flux directly, especially without the need for heating the probe used in the measurements.